Abstract:

The internal resistance of lithium-ion battery is the core index to evaluate the working state of the battery.The existing model is difficult to reflect the dynamic change law of internal resistance,and lacks the quantitative relationship between internal resistance and health status.In order to reveal the influence of charge-discharge rate,state of charge (SOC) and electrode thickness on internal resistance,a one-dimensional electrochemical simulation model of graphite/NMC111 lithium-ion battery is constructed.Based on the hybrid pulse power characteristic (HPPC) test standard,the simulation is carried out in the range of 0.50C-2.00C,10%-90% SOC and 25-65 μm electrode thickness.The variation of ohmic internal resistance and polarization internal resistance is analyzed by voltage loss decomposition method.The results show that the increase of electrode thickness will significantly increase the ohmic internal resistance and polarization internal resistance.The internal resistance of the battery is strongly nonlinear with SOC,and rises sharply in the range of low SOC (≤25%) and high SOC (≥90%).The increase of discharge rate will accelerate the growth of concentration polarization internal resistance.The research results provide a theoretical basis for battery structure optimization and BMS parameter design.

Key words: lithium-ion batteries, internal resistance characteristics, electrode thickness, discharge rate, state of charge (SOC)